In underground mining operations, an access tunnel is bored into or beneath the earth, and miners and their equipment are introduced to extract coal, limestone, precious metals and other minerals from product-bearing seams. Such mining operations may involve blasting into the face of a seam and/or the use of digging equipment to dig into the face. Such activities create instabilities in the walls of the mine, especially in the roof (also known as the “back”), as the equipment is advanced and the products of mining are removed, regardless of whether the mining is carried out by room-and-pillar methods, longwall methods or other methods. Such instabilities create a risk of roof falls and wall (or pillar) collapse, which may put the miners and their equipment in jeopardy.
Scaling is a process by which loose and fractured materials may be removed from the roof and walls of a mine as a part of the mining, cycle. Typically, scaling has been accomplished in several ways. The earliest known method, which is still practiced today, involves manually using a pry bar from the mine floor or from a scissor lift or manbasket boom to remove the loose material. This method is slow, inefficient, and can subject the scaling personnel to danger from falling materials. Another method involves the application of a stream of high-pressure water to the mine roof or walls; however, this method may not remove all fractured materials, and it presents the related problems of providing a supply of water and providing for its disposal.
Mechanical pick-type scaling machines are known by which machines employ a prying tool to which a static force is applied to remove material. Typically, these machines apply force to the prying tool by means of a hydraulic cylinder or actuator. These machines are typically much faster than manual scaling operations; however, the large forces applied by such machines may create additional stress cracks and other unstable conditions, which may lead to roof falls that damage or block the machines and mine personnel. In addition, mechanical pick-type scaling machines are more suited to use in layered rock formations such as limestone, and may not be efficient when used in other types of formations.
Conventional hydraulic breaker machines are also known for applying a series of hammer or impact blows to a tool in a generally downward direction to break rocks on a floor surface or to break up the floor surface itself. These machines operate by the application of a series of hammer blows to a tool, generally by the action of a reciprocating hydraulic actuator. Breaker-style scaling machines are known by which the hammer head of a hydraulic breaker machine is mounted on a boom so that the tool may be applied to a roof or wall surface for scaling purposes. Such breaker-style machines generally do not permit good visibility of the working surface by the operator, and they can also result in the application of too much energy to the rock, causing additional stress cracks (which require additional scaling) and falls. Furthermore, such breaker-style machines typically operate in such a manner as to apply forces to the boom in a direction that is not aligned with the axis of the boom. Consequently, such machines may create severe reaction forces in the knuckle joints of the boom, leading to excessive wear and vibration and a reduced service life.
It would be desirable, therefore, if a scaling device could be developed that would avoid some of the problems of known scaling systems.